1. Field of the Invention
The present invention relates vapor deposition apparatus and method for forming a thin film, and more particularly to vapor deposition apparatus and method which are applied to a process for manufacturing a semiconductor wafer substrate to which high quality is required, and which can suppress occurrence of contaminants such as particles, etc. in vapor phase and deposits on the wall of a reactor to thereby form a thin film having uniform film thickness, so that a homogeneous semiconductor wafer having no dispersion in resistance value and little crystal defect.
2. Description of the Related Art
FIG. 14 shows a conventional vapor deposition apparatus for forming a thin film. In FIG. 14, a rotational substrate holder 82 for mounting a wafer substrate 81 such as a silicon wafer or the like, a rotational shaft 83 for rotating the rotational substrate holder 82 and a heater 84 for heating are generally disposed at the lower portion in a cylindrical reactor 80, and a rotating motor (not shown) is connected to the rotational shaft 83. Further, plural exhaust ports 85 for exhausting non-reacted gas, etc. are disposed at the bottom portion of the reactor 80 and connected to an exhaust control device (not shown). Further, plural gas supply pipes 86 for supplying raw-material gas and carrier gas into the reactor and a disc-shaped straightening vane 87 are provided at the top portion of the reactor 80. The straightening vane 87 is perforated with many holes 87a for regulating flow of gas.
The conventional vapor deposition apparatus is constructed as described above, and the substrate 81 mounted on the rotational substrate holder 82 which is rotated at a predetermined rotational number by the rotation of the motor is heated to a predetermined temperature by the heater 84 while rotated. At the same time, reaction gas such as raw-material gas, carrier gas, etc. are introduced through the plural gas supply pipes 86 into the reactor 80 to make the momentum of the gas and the pressure distribution uniform, and then passed through the many holes 87a of the straightening vane so that the gas flow-rate distribution in the reactor is uniform, whereby the reaction gas is uniformly supplied onto the wafer substrate 81 on the rotational substrate holder 82 to grow a thin film in vapor phase.
In the vapor deposition apparatus for forming a thin film on a semiconductor wafer as described above, various proposals have been made to prevent occurrence of particles and adhesion of deposits to the inner wall of the reactor due to the thin film forming gas, and also to prevent occurrence of crystal defects due to some troubles in a thin film forming process to thereby obtain a wafer having a thin film which is homogenous and uniform in film thickness. For example, in Japanese Laid-open Patent Application No. Hei-5-74719, the supply flow amount of the raw-material gas is controlled to a predetermined value to prevent the temperature variation in the reactor, thereby suppressing crystal defects. In Japanese Laid-open Patent Application No. Hei-5-90167, the raw-material gas amount, the pressure in the reactor, the rotational number of the rotational substrate holder, etc. are controlled to predetermined values so that the in-plane temperature distribution of the wafer substrate in the thin film forming process is made uniform, thereby preventing slip. In Japanese Laid-open Patent Application No. Hei-6-216045, a part of the inner wall of the reactor in which deposits are liable to occur is provided with a shielding pipe while the inner peripheral surface thereof is kept smoothened, thereby facilitating a cleaning work of the reactor after the thin film forming operation is performed and also the gas flow is kept to a laminar flow state to form a homogenous thin film. Further, in Japanese Laid-open Patent Application No. Hei-7-50260, a method of introducing the raw-material gas and the carrier gas into the reactor is set to a predetermined one to thereby make uniform the gas momentum and the gas pressure, whereby the raw-material gas, etc. are supplied onto the substrate at a uniform flow rate to make the film thickness uniform.
However, the various proposed conventional vapor deposition apparatuses as described above have not yet been cable of sufficiently preventing troubles such as the occurrence of the crystal defect, the adhesion of particles on a wafer substrate on which a thin film is formed, etc. Further, particularly, following recent ultra-high integration of semiconductors, higher quality has been increasingly required to wafer substrates, and reduction in quality due to a slight defect on a thin-film formed wafer substrate induces a critical problem in many cases.